A hybrid electric vehicle (HEV) can be propelled by an engine and a traction battery. A plug-in hybrid electric vehicle (PHEV) includes a traction battery that can be charged via electrically connection to an external power source. A battery electric vehicle (BEV) does not include an engine and is propelled only by a traction battery. HEV's, PHEV's and BEV's are three examples of vehicles that are at least partially propelled by a traction battery. In such applications, the traction battery can include a battery pack having individual cells that are charged and discharged during operation. The traction battery may also discharge electric power from and transfer electric power between the cells during cell balancing operations.